Section 4: Bioprocess Engineering and Process Biotechnology
Mass transfer in bioprocesses (kLa)
Subtopic: Fundamentals of Mass transfer in bioprocesses (kLa)
Question Statement:
In Neurospora crassa, a mutation in the poky gene results in a slow growth
phenotype (poky). The results of four crosses are given below.
(1) wild-type f x wild-type ® → All progeny are wild-type
(2) wild-type f x poky & → All progeny are wild-type
(3) poky f x wild-type & → All progeny are poky
(4) poky f x poky & → All progeny are poky
Which one of the following explains the inheritance mode of poky?
Options:
(A) Episomal inheritance
(B) Mendelian inheritance
(C) | Mitochondrial inheritance
(D) X-linked inheritance
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2021 Q.43)**
**1. Governing Concept**:
- **Topic**: Non-Mendelian Genetics & Cytoplasmic Inheritance
- In *Neurospora crassa*, sexual crosses involve a female (protoperithecial parent, $\text{fem}$) providing the majority of cytoplasm, and a male (conidial parent, $\text{male}$).
- Examining the crosses:
- (2) $\text{wild-type} \ (\text{fem}) \times \text{poky} \ (\text{male}) \rightarrow \text{All wild-type}$
- (3) $\text{poky} \ (\text{fem}) \times \text{wild-type} \ (\text{male}) \rightarrow \text{All poky}$
- The progeny phenotype is dictated exclusively by the maternal/female parent (maternal inheritance).
- The *poky* phenotype is caused by a mutation in the mitochondrial DNA (mtDNA) affecting ribosomal subunits, following **mitochondrial (maternal cytoplasmic) inheritance**.
**2. Option Analysis**:
- **Option (A) [Episomal inheritance] is INCORRECT**: Bacterial plasmid mechanism.
- **Option (B) [Mendelian inheritance] is INCORRECT**: Mendelian crosses yield equal segregation ($1:1$ in haploid ascomycetes).
- **Option (C) [Mitochondrial inheritance] is CORRECT**: Maternal transmission of mitochondrial genome mutations in *Neurospora*.
- **Option (D) [X-linked inheritance] is INCORRECT**: Fungi lack mammalian XY sex chromosomes.
**3. Final Answer**:
- **Correct Choice**: **C**
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